Freezing unit



FRANKLIN ETAL pril 16, 195

5 Sheets 5 1 Filed June 19, 1953 u 5w 6 L r W man 4, m n w. .v M

April 1957 E. w. FRANKLIN ET AL 2,788,641

FREEZING UN IT FildJune 19, 1955 5 Sheets-Sheet 4 INVENTORS ELaEer W. Aka/yum BY Giana; Ova/era- April 16, 1957 Filed June 19, 1953 E. W. FRANKLIN ET AL FREEZING UNIT 5 Sheets-Sheet 5 GEORGE Or era/v BY 6 J m w United States Patent FREEZING UNIT Elbert W. Franklin and George Overton, Los Angeles, Calif., assignors to Freez-Aire Corp. of America, Los Augeles, Calif., a corporation Application June 19, 1953, Serial No. 362,818

14 Claims. (Cl. 62-4) This invention relates to freezing units and more particularly to an improved home freezer operating at 32 F. and below and incorporating a forced cold air circulation system.

Heretofore freezing units used in homes have employed cold coils within or around the main shell for maintaining the temperature of the unit at the desired sub-freezing value. There are certain advantages however in employing forced cold air circulation refrigeration as opposed to cold coils. Among the most important of these advantages is the fact that a much moreuniform temperature can be maintained throughout the interior region of the unit. This is because the cold refrigerating air can easily pass through all spaces within the unit whereas the cold coils are necessarily stationary. Even though several cold coils may be uniformly spaced about the interior walls,

, it is still difficult to maintain a uniform temperature in the central regions.

Another important advantage of the cold air circulation system results from the constant air circulation throughout the interior of the unit whereby the cold air is forced into direct heat transfer contact with all of the food products within the unit. Additionally, the air circulation system permits a higher relative humidity to be carried.

A further advantage of the cold air circulating system is the elimination of complex coil piping systems thereby rendering the defrosting problem enormously simplified.

It is a primary object of the present invention accordingly, to provide a home freezer unit incorporating a cold air circulation system for maintaining a substantially uniform temperature below 32 F. entirely throughout the interior region of the freezing compartment or cold storage cabinet and yet keep food therein free from frost. A feature of the invention additionally provides means for passing a greater quantity of cold air across the upper levels than across the lower levels of the cold storage cabinet whereby the temperature gradient tending to exist from the lower levels to the upper levels is compensated.

Another object is to provide means in the freezer unit cold storage cabinet for preventing blocking of the air circulation by food products placed therein.

Another principal object of the invention is to provide a cold air refrigeration apparatus incorporating an improved expanding capillary tube system in the evaporator in place of more complex expansion valves. including novel means for insuring uniform expansion of the liquid refrigerant in the evaporator from the end of the capillary tube.

Another object is to provide a freezer unit which is well adapted to automatic defrost of the evaporator coils.

An auxiliary object is to increase greatly the efficiency of the cold air refrigeration apparatus by placing the various apparatus components in positions to effect effi- 1, Gient heat exchanges.

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Still another object of the invention is to provide a completely automatic defrosting system adapted to be placed in operation in response to the amount of frost that has built up on the evaporator. In the past, such automatic defrosting has usually been effected periodically by timing clocks. In such systems the defrosting mechanism would operate regardless of whether defrosting were actually necessary. In the present invention, the defrosting system only operates when actual defrosting is necessary to insure continued efiicient operation.

Yet another important object is to provide a novel system for disposing of the defrost condensate. Heretofore such defrost condensate liquid would collect in a pan and have to be emptied periodically.

These and additional objects and advantages of the invention will be better understood by referring to the accompanying drawings illustrating a preferred embodiment of the freezer, in which:

Fig. l is a perspective view of the cold storage housing or cabinet and the refrigeration apparatus with certain portions cut away to expose various components of the unit;

Fig. 2 is an elevational cross-sectional view of the freezing unit illustrating the cold air circulation system;

Fig. 3 is an enlarged View of the portion enclosed by the circular arrow 3 in Fig. 2;

Fig. 4 is a cross-sectional view of the cold storage cabinet as seen along the line 44 of Fig. 2;

Fig. 5 is a highly schematic layout of the various components of the refrigeration apparatus useful in explaining the operation of the system;

Fig. 6 is another cross-sectional view as seen along the line 66 of Fig. 2;

Fig. 7 is an elevational view partly in section as seen looking in the direction of the arrow 7 in Fig. 6;-

Fig. 8 illustrates a portion of the evaporator unit in the cold air refrigeration apparatus;

Fig. 9 shows another view of the evaporator unit as seen along the line 9-9 of Fig. 8;

Fig. 10 is an enlarged view of the portion enclosed by the circular arrow 10 in Fig. 9 and Fig. 11 is another schematic view showing a portion of the electrical system for automatic defrosting of the refrigeration apparatus.

In the several drawings, like components are designated by like reference numerals. Figs. 1 to 4 relate generally to the cold air circulation system and Figs. 5 through 11 relate to the cold air refrigeration apparatus and defrosting system.

Referring to Fig. 1, the freezing unit comprises a cold storage housing or cabinet 10 provided with a door 11 for easy access and two vertical sidewalls 12 and 13. The cabinet 10 is preferably of the upstanding type and in cludes in its base support the refrigeration and defrosting apparatus designated generally by the numeral 14.

Cold air circulation system.To maintain the interior of the insulated cabinet 10 at a substantially uniform subfreezing temperature, there is provided a cold air circulation system comprising a blower 15 disposed in the base of the cabinet and adapted to pass cold air through the interior of the cabinet in a closed circulation path.

As more clearly shown in Fig. 2, this air circulation is accomplished by providing a vertical passage 20 in the first sidewall 12 through which cold air may pass from the blower 15 to the interior of the cabinet, and a second vertical passage 21 in the wall 13 for returning the air to the blower. A horizontal passageway 21a leads from the bottom of return passageway 21 to an evaporator through which the air passes before returning to the blower 15 as will later be described. As shown, the various levels of the cabinet interior may be sectioned otfby means-ofshelves "22. The first passage is pro- 'vided with a-series of vertically spaced openings'23 communicating with the interior of the cabinet, each opening being provided With a spaced baffle member 24, the purpose for which will be described shortly. Similarly,

" t the second 'wall passage-21 includes'a plurality of vertically "into the opening asxwellas through the holes 30. The

' several'baflie plates as shownin both Figs. 1 and 2 prevent the blocking of the various openings. by food products placed on the shelves and also tend to distribute the cold .-air more'uniforrnly.

In a-freezing unit having asubstantiahvertical height as in the present case, there is a tendency for" the cold air to migrate to the lower levels of the interior and the warmer air tocollect in the upper levels. In order to overcome this temperature gradient increasingfrom the lower to the upper levels, the first air passage 20 may be "partitioned by a partition wall- 40 to form' first and ,secondvertical air passagesv 41 and'42 as clearly seen in'Fig. 4.

Referring again to Fig. 1, it will be seen that the first ---vertical passage 41 has two verticallyspaced openings 23 communicating 'with'the lower half of the interior of the cabinet, whilet-he second vertical passage 42.,has two openings communicating with the upper half. An additional opening in the first'vertic'al passage 41 is also provided communicating with the upper half of the interior whereby there are a total of three openings in the; upper levels as compared to onlyv two openings inthe lower levels. The baffle plates 24; however, are. adapted to 9 cover the same area on either side of the. partition wall 40 to provide a symmetrical appearance. Thus, there are actually no openings, behind certain portions of some of the baffle plates, these points being'designated by the letters-D in Fig. 1. From the above described construction it will be. readily apparent that more cold air is permitted to enter the upper regions of the cabinet interior than the lower regions.

In the operation of the air circulation system, the blower 15, as shown in"Fig. 2, will pass. cold air up through the first wall passage 20 to passout the various -openings23 and across the interior of the cabinet at --'various levels as indicated by the arrows. This air will then pass into the openings 25 in the second sidewall passage 21 to pass'downthis passage back to the blower 1 '15." Since-there are more openings at. the. upper.1evels than at the lower levels, more cold fair will. be passing *across the-upper regions to .compfinsate for the. referred uto temperature gradient which tends to exist. As. a result the temperature is substantially uniform throughout the --entire vertical length .of the cabinet. It should also be noted thatthe air is circulated in a closed path. and thus all of the air within the storage cabinet is forced to move continuously.

- Cold-air refrigeration apparatus.-Referring nowto Fig. 5,- the cold. air refrigeration apparatus, designated generally by the numeral 1 4, in Fig. l is ,shownin a schematic layout for purposes of clarity. This apparatus --comprises-a compressor SOdriven by a'motor 51-and connected through an outletv conduit; 52.,past a..defrost evaporator thepurpose .ofwhichwill-.be explainedsubsequently. .Conduit v52 then passes through, condenser 53 andinto abalancingtank 54. -Acapillaryg tube-55 .tlommunicates withytheabalancing tankv54z-and. follows a winding path-..termina ting -in.=.ancevaporatori-56 provided with suitable cooling fins 57. The outlet conduit 58 from the'"evaporator 56 passes into a liquid trap '59 a'sshown.

From the liquid trap 59 there is provided a return conduit 64) passing back to the compressor 50. The evaporator 57 includes a plurality of coil turns 61 connected between the termination point of the capillary tube 55 and the evaporator outlet conduit-F558.

Referring to Fig. 6.the.relative position of these various components is shown in apreferred arrangement, the

zcoiled turns .61 int-he evaporator -56 beingnclearlyrshown. :ln Fig. .7, which-:;-illustratesathe:cornponentstshown in Fig. 6 looking in the direction of the arrow 7'," there is shownthecondenser housing 53 within which the conduit52 is coiled. A motor 71 adapted to drive a fan 72 is disposed adja'eentrt-he'.condenser.53 to blow air over these coils. The balancing tank 54, as shown in Fig. 7, comprises an elongated closed chamber having its inlet opening for the conduit 52 disposed at a level higher than .the outlet opening for the capillary tube '55. As shown,

this balancing tank is partiallyifilled with a compressible gas such as a gaseous refrigerant.

Figs. 8 and 9 show, in greater detail, views of the evaporator 56 and liquid trap '59. i It will be seen that 25 the outlet conduit 58 from the coiled turns 61' inthe evaporator terminates in' the liquid trap '59 adjacent the top thereof, the return coi1duit'60 also communicating with the upper portion of the liquid trap. This arrangement permits any liquid dripping from the end 'ofthe outlet conduit 58 from getting into the return conduit 69, such liquid collecting at the bottom of the liquid trap The terminating end of the capillary tube 55 in the evaporator 56 is shown enlarged in Fig. 10,the terminating end of the capillarytube projecting. into the coiled turns 61 of theevapo'ra'tor a given distance'whereby liquid refrigerant passing out the end' of the capillary tube will expand into the coiled turns.

Referring once again to Fig. 5 the operation of the cold air refrigerating apparatus is as follows:

A suitable refrigerating gas is compressed by the compressoreausing' the temperature of the compressed gas to'rise to a value of about 150 F. This hot com pressed gas is passed through the conduit 52 surrounding a portion of the defrost evaporator housing'in'to'the con- 45..

denser 53-where it is cooled by the fan 72' blowing cold air across the variousturns of the conduit 52-within the condenser housing. This'cooling causes the compressed gas to liquify, the liquified' refrigerant passinginto the balancing tank-54. From the balancing'tank 54'the liquid refrigerant passes through thecapillary tube terminating -within-the coiled turns 61 'in' theevaporator 56. The expansion of the liquified refrigerant" in the evaporator is ordinarily controlled by anexpansion type valve in order to keep the expansion uniform.

Inaccordance with a feature of the invention this 'ex- =pansio1rvalve is replaced by the-capillary" tube 55' from the end' ofwhich an expansion of the" liquid'refrigerant takes place. It has been found however, that the use of a capillary tube for expanding the'liquid refrigerant results inerratic expansion and in order to render'the expansion more uniform, there is provided 'theipreviously referred to balancing tank 54 betwcenthe coir denser 53 and'the capillary tube 55. This balancing ant expansion at the end of the capillary tube substantially uniform.

Throughout the various coiled turns 61 in the evaporator 56, the liquified refrigerant will evaporate thereby absorbing considerable heat from the surrounding cooling fins 57. Air is caused to flow over these cooling fins 57 before returning to the blower 15 and is therefore cooled down to a temperature substantially below freezing before passing through the vertical passages in the cabinet walls. The expanded gaseous refrigerant, which is at this time itself quite cold being in the neighborhood of 30 P., passes through the liquid trap 59 and the return conduit 60 to the compressor. This gas is then recompressed by the compressor and the cycle repeated.

It will be noted in the various figures that the capillary tube 55 leading from the balancing tank 54 is wrapped around the return conduit 60. This arrangement provides a heat exchanging means whereby the cold refrigerant gas passing back to the compressor through the conduit 60 will absorb heat from the relatively hotter liquified refrigerant passing through the capillary tube 55. Such heat exchange insures the maximum heat exchange efficiency and is a further safeguard against any refrigerant being in the liquid state when it is returned to the compressor.

Defrosting system.-Referring once again to Fig. 5,

the defrosting system for removing coatings of frost which tend to accumulate on the coils of evaporator 56 thereby insulating it and rendering the refrigeration apparatus less efiicient, includes a conduit 62 coupled through a T-joint 63 to the conduit 52 hearing hot compressed gas from the compressor 50 to the condenser 53. The conduit 62 passes under a defrost condensate collecting container or pan 64 and terminates in an opening 65 in the coiled turn 61 in the evaporator, as clearly shown. in Fig. 10. The condenser and capillary tube 55 are thus bypassed by this conduit 62.

From the defrost condensate collecting container or pan 64 there is provided a conduit 67 serving to pass the defrost condensate into the defrost evaporator 68.

As shown more clearly in Fig. 6, the defrost evaporator comprises a semi-closed housing partially surrounded by a portion of the compressor outlet conduit 52. This portion of the conduit 52 is designated by the numeral 52 and is turned back on itself to cover a substantial area of the lower portion of the housing. The defrost evaporator housing is open at the top at 68' and is adapted to be lifted from the cradling conduit portions 52' for cleaning.

Disposed in the conduit 62 is a solenoid operated valve V normally closing the conduit and adapted to be operated to initiate the defrosting system in response to the quantity of frost built up on the evaporator.

This valve V is connected by .a pair of conductors 73 to a switch S adapted to be thrown in different positions by a pressure bellows 74 operable in response to the amount of frost on the evaporator 56. This actuation is effected by a small capillary tube 75 terminating in a thermally responsive temperature bulb 76 as shown in Fig. 5. Input power lines 77 also connect to the switch S.

In the operation of the defrosting system, assume that a sufficient coating of frost has built up on the evaporator as to render the cooling of air blown thereover less efficient. Due to the insulative effects of the ice coating, the expanded refrigerant passing out of the evaporator outlet conduit 58 will be at a somewhat lower temperature than normal. This lower temperature serves to contract fiuid in the thermal bulb 76 disposed against the outlet, such contraction being communicated through the small capillary tube 75 to operate the bellows 74.

' Operation of this bellows throws the switch arm to the dotted line position shown in Fig. 5 to connect the power line to the valve V opening the normally closed conduit Because the conduit 62 is substantially larger in diameter than the small capillary tube 55, most of the hot compressed refrigerant gas from the compressor 50 will pass through this tube 62 bypassing the condenser 53 and capillary tube 55 to pass directly into the evaporator. The high temperature of this hot gas will effectively defrost any frost coating on the evaporator, the defrost condensate dropping into the collector container 64. As soon as the evaporator reaches a temperature of 36 to 40 R, which indicates a complete elimination of frost on the evaporator, the temperature of the refrigerant gas in conduit 58 will have increased sufiiciently to cause expansion of the fluid in the thermal bulb 76 thereby operating the bellows to throw the arm of switch S back into its solid line position. The solenoid operated valve V is thereby closed and hot compressed gas from the compressor 50 will pass through the conduit 52 and capillary tube 55 to restore the refrigeration apparatus to normal operation.

The water from the frost collected in the container 64 passes by gravity out the conduit 67 to the defrost evaporator housing. In Fig. 7 the relative positions of the defrost evaporator 68 is shown disposed at a lower level than the other components, whereby this gravity flow may take place. Because of the relatively high temperature in the defrost evaporator due to the conduit portion 52 disposed adjacent thereto, the defrost condensate liquid will be evaporated, passing out the top opening 68' into the surrounding atmosphere. The arrangement thus permits the complete disposal of the defrost condensate liquid, and periodic emptying of the collecting pan or container 64 is avoided.

It will be noted that the normally closed bypass conduit 62 is bonded to the collector pan 64. The hot compressed gas passing through this conduit will therefore serve to raise the collecting pan temperature to 33 F. or above, thereby causing the condensate to remain in a liquid state and flow through the drain conduit 67 to the defrost evaporator 68.

Alternative to the temperature responsive thermal element for operating the defrosting system solenoid valve V in the normally closed conduit 62, there may be provided a pressure control means. Referring to Fig. 11, the bellows 74 may be actuated by a small capillary line 110 connected into the return conduit 60 by means of the T-joint 111. When a large coating of frost builds up on the evaporator, the pressure in the return conduit 60 of the cold refrigerating gas will drop, actuating the bellows 74 to throw the switch S into the dotted line position to start the defrosting cycle as previously described. After the evaporator has been completely defrosted, the pressure in the line will build up, actuating the bellows 74 to bring the switch back to its normal solid line position.

It is to be noted at this point that the novel defrosting system herein described is not necessarily limited to use with the particular refrigeration apparatus described. It may be used on more complex types of commercial refrigeration and in multiple unit installations. Because it is operable in direct response to the amount of frost on the cooling coils it is more positive and eflicient than any prior types of automatic defrosting systems.

Cold control system.-As shown in Figs. 5 and 11 there may be provided an additional switch for controlling the operation of compressor 50 and blower 15 in accordance with the temperature within the refrigeration cabinet. To accomplish this automatically there is provided a pair of conductors 78 tapped from the main power input conductors 77 connecting into a switch from which additional conductors 79 pass to the compressor motor and blower.

The switch 80 is adapted to be controlled in response to the temperature within the upper rear portion of the refrigeration cabinet by means of a small capillary line 81 connecting to a thermal bulb 82. The actual disposition of the switch 80, capillary tube 81, and bulb 82 is passing compressed gas to the condenser for condensation into a liquid, an evaporator for evaporating the liquid refrigerant and a connecting conduit between said condenser and said evaporator; a defrosting system for removing frost tending to accumulate on the evaporator comprising: a normally closed conduit for passing compressed gas from the compressor directly to the evaporator whereby said condenser is bypassed, said normally closed conduit being of substantially larger size than said connecting conduit, and means for opening said normally closed conduit automatically operating in response to a given temperature of the refrigerant passing out of the evaporator and including temperature sensitive means disposed adjacent the outlet of the evaporator.

12. In a freezing unit, a forced cold air circulation system comprising: an upstanding cabinet having first and second vertical side walls each having a passage communicating with the interior of the cabinet through a series of vertically spaced openings; and means for passing cold air through one passage, out its openings, across the cabinet interior, through the second wall passage openings, and through the second wall passage, there being more openings in the first side wall passage adjacent the upper interior portion of the cabinet than adjacent the lower interior portion whereby more cold air passes into the upper levels of the cabinet than the lower levels, a bafiie plate member for each of said openings and means supporting each bafiie plate member in spaced relationship to its corresponding opening and within said cabinet whereby air passing through an opening passes about all of the edges of the baflie plate member associated with such opening in a divided flow.

13. In a freezing unit, a forced cold air circulation system comprising: an upstanding cabinet having marginal Walls defining a vertically elongated interior chamber, at least one of said walls carrying a discharge passageway leading upwardly from the bottom of the cabinet, said discharge passageway having aperture means placing said discharge passageway in communication with said chamber, said aperture means providing a predetermined total cross-sectional fiow area from said discharge passageway into said chamber with a first predetermined portion of said flow area being disposed adjacent the lower end of said chamber and a second predetermined portion of said flow area being disposed adjacent the upper end of said chamber, said second predetermined portion being greater than said first predetermined portion to provide for increased air circulation from said discharge passageway into the upper portion of said chamber than occurs in the lower portion of said chamber to maintain a uniform temperature gradient within the chamber, at least one of said walls carrying a return passageway leading downwardly to the bottom of the said cabinet, said return passageway having return aperture means placing said return passageway in communication with said chamber to provide a predetermined cross-sectional flow area from said chamber into said return passageway, and means mounted in the bottom of the cabinet for passing cold air upwardly through the discharge passageway and out through said aperture means into said chamber, through said chamber and into said return aperture means and said return passageway in a closed circulation path.

14. In a freezing unit, a forced cold air circulation system comprising: an upstanding cabinet halving marginal walls defining a vertically elongated interior chamber, at least one of said walls carrying a discharge passageway leading upwardly from the bottom of the cabinet, said discharge passageway having a plurality of upper discharge openings disposed adjacent the upper end of said chamber and at least one lower discharge opening disposed adjacent the lower end of said chamber, said upper discharge openings providing a larger cross-sectional flow area than the cross-sectional flow area of said lower discharge opening to provide for increased air circulation from said discharge passageway into said chamber in the upper portion of said chamber than occurs in the lower portion of said chamber to maintain a uniform temperature gradient within the chamber, at least one of said walls carrying a return passageway leading downwardly to the bottom of said cabinet, said return passageway having return openings placing said return passageway in communication with said chamber to provide a predetermined cross-sectional flow area from said chamber into said return passageway, and means mounted in the bottom of the cabinet for passing cold air upwardly through the discharge passageway and out through said discharge openings into said chamber, through said chamber and into said return openings and said return passageway in a closed circulation path.

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